When you complete Webster Street the Thermal Breather becomes unlocked. The Thermal Breather prevents you from losing health from inhaling fumes and also picks out heat sources so you can find people easier.

Press UP,UP,DOWN,DOWN,CIRCLE,DOWN,UP,CIRCLE at the main menu screen. A "CHEAT" option will be avaiable at the title screen. Enter one of these codes to activate. You can then toggle them on or off (except all levels and emergencies) and all codes must be entered in uppercase.